Re: [PATCH v4 1/2] rcu: Make expedited RCU CPU stall warnings detect stall-end races

[Borislav Petkov]

On Mon, Dec 29, 2025 at 11:16:15AM -0800, Paul E. McKenney wrote:
> If an expedited RCU CPU stall ends just at the stall-warning timeout,
> the current code will print an expedited stall-warning message, but one
> that doesn't identify any CPUs or tasks causing the stall.  This is most
> likely to happen for short-timeout stalls, for example, the 20-millisecond
> timeouts that are sometimes used for small embedded devices.  Needless to
> say, these semi-empty stall-warning messages can be rather confusing.
> 
> One option would be to suppress the stall-warning message entirely in
> this case, but the near-miss information can be quite valuable.
> 
> This commit therefore detects this race condition and emits a "INFO:

s/This commit therefore detects this/Detect this/

> Expedited stall ended before state dump start" message to clarify matters.
> 
> Reported-by: Borislav Petkov <bp@xxxxxxxxx>
> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
> ---
>  kernel/rcu/tree_exp.h | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)

But yeah, makes sense.

Acked-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>

Thx.

-- 
Regards/Gruss,
    Boris.

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